A giant waxy monkey tree frog (Phyllomedusa bicolor) in Rupununi, Guyana. Photo by Marlondag/FAO

Initiatives to protect tropical forests are on the rise as countries strive to meet their climate, biodiversity and sustainable development commitments. However, little is known about the factors that drive the success of conservation initiatives in different locations, leaving policymakers and practitioners in the dark about how to improve them.

Traditional impact evaluations analyze whether interventions reduce overall forest loss compared to a business-as-usual scenario, but fail to explain where, how, and under which conditions they can achieve better results. In the past two decades, experts have increasingly recognized the need to understand how different contexts, design options, and implementation choices affect conservation efforts. So, what have we learned about the factors that shape the effectiveness of forest conservation interventions?

To find out, researchers at the Center for International Forestry Research and World Agroforestry (CIFOR-ICRAF) examined 47 peer-reviewed papers selected from a pool of 1,486 studies. The papers, which compare intervention and control areas, look at forest conservation initiatives including incentives, disincentives, and enabling measures.

“A conclusion from our review is that interventions achieve greater results where forests are under higher risk of deforestation—for example, due to the expansion of the agricultural frontier—meaning that policymakers and practitioners should prioritize those areas,” said lead author Cauê Carrillho, who conducted the research as part of CIFOR’s Global Comparative Study on REDD+.

But the analysis also brought to light another realization: drawing additional conclusions on how different factors influence forest conservation outcomes requires a larger and more diverse body of research. Existing studies tend to focus on two types of interventions (protected areas and payment for ecosystem services (PES)); the effects of context (e.g. governance, proximity to roads, poverty levels); and initiatives taking place in Latin America, especially in Brazil.

“Impact evaluations should assess the influence of different factors in a systematic, continuous manner,” said co-author Colas Chervier, a researcher in ecological economics at the French Agricultural Research Centre for International Development (CIRAD) seconded to CIFOR-ICRAF. “Building this evidence base is crucial to advance our collective understanding of what works where, and how to make the most of the existing budgets for forest conservation.” 

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More insights for better policies

As part of the review, CIFOR researchers identified key categories related to intervention design and implementation: the type of implementer (e.g. national versus subnational level); the duration and size of the intervention; and the management styles used, such as the extent to which humans are allowed within protected areas, or whether PES are made to individuals or communities.

The scientists also listed contextual aspects that can affect outcomes, including population size, poverty levels, proximity of forests to roads, forest loss rates, suitability of the land for agriculture, and governance (e.g. PES programmes tend to work better where property rights are well-defined.) 

The small number of available studies for most of those factors, and the difficulty in isolating the effects of single factors, mean it is not yet possible to draw general conclusions. But in providing a state of play, authors believe the review can serve as a starting point to take impact evaluations to the next level. 

For Carrillho, one way to make future studies more robust and nuanced, especially where there is limited access to data, is by resorting to both qualitative and quantitative approaches: “Studies that provide more complex, detailed insights can help policymakers and practitioners finetune and adequately combine existing interventions, instead of discarding them altogether.”